/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

@file:JvmName("CoroutinesUtils")
package org.springframework.core

import kotlinx.coroutines.Deferred
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.FlowPreview
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.async
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.reactive.awaitFirstOrNull
import kotlinx.coroutines.reactive.flow.asPublisher

import kotlinx.coroutines.reactor.mono
import reactor.core.publisher.Mono
import reactor.core.publisher.onErrorMap
import java.lang.reflect.InvocationTargetException
import java.lang.reflect.Method
import kotlin.reflect.full.callSuspend
import kotlin.reflect.jvm.kotlinFunction

/**
 * Convert a [Deferred] instance to a [Mono] one.
 *
 * @author Sebastien Deleuze
 * @since 5.2
 */
internal fun <T: Any> deferredToMono(source: Deferred<T>) =
		GlobalScope.mono(Dispatchers.Unconfined) { source.await() }

/**
 * Convert a [Mono] instance to a [Deferred] one.
 *
 * @author Sebastien Deleuze
 * @since 5.2
 */
internal fun <T: Any> monoToDeferred(source: Mono<T>) =
		GlobalScope.async(Dispatchers.Unconfined) { source.awaitFirstOrNull() }

/**
 * Invoke an handler method converting suspending method to [Mono] or
 * [reactor.core.publisher.Flux] if necessary.
 *
 * @author Sebastien Deleuze
 * @since 5.2
 */
@Suppress("UNCHECKED_CAST")
@FlowPreview
internal fun invokeHandlerMethod(method: Method, bean: Any, vararg args: Any?): Any? {
	val function = method.kotlinFunction!!
	return if (function.isSuspend) {
		val mono = GlobalScope.mono(Dispatchers.Unconfined) {
			function.callSuspend(bean, *args.sliceArray(0..(args.size-2)))
					.let { if (it == Unit) null else it }
		}.onErrorMap(InvocationTargetException::class) { it.targetException }
		if (function.returnType.classifier == Flow::class) {
			mono.flatMapMany { (it as Flow<Any>).asPublisher() }
		}
		else {
			mono
		}
	}
	else {
		function.call(bean, *args)
	}
}
